It's the flat white, the Australian answer to the latte, and it's a name you should know the next time your local barista asks, "What's your poison?" Over the past few years in the U.S., it's gone from being a complete unknown coffee drink to being the next big thing in caffeine.

"I was in London on business in the fall of 2013 when an Australian colleague brought me to a coffee place at Canary Wharf," says Jason Fox, the global head of product, technology, and program management at Reuters News Agency. "She ordered something called a 'flat white,' and I had no idea what it was, but she raved about it, and I got one too. I was hooked."

When he returned to the U.S., Fox's flat-white jones couldn't be sated—at first. Now it seems to be everywhere he looks.

"When I first got back to New York after that initial trip and asked for a flat white, baristas looked at me like I was speaking a different language," he says. "But a year later, it seems every coffee place now has its own take on a flat white."

So what's so addictive about this seemingly innocuous coffee drink that could easily be mistaken for a latte or a cappuccino by the non-coffeescenti?

It's all about the milk.

Cappuccino on the left, flat white on the right. Photo: Michael Y. Park

"It's like a cappuccino, except that instead of a top layer of flavorless, airy, milky foam, it's a velvety, dense foam that is mixed evenly through the drink," Fox says.

The flat white was birthed in Australia in the 1980s, where a cappuccino has a noticeably drier foam top than the cappuccino Americans know and is often sprinkled with cocoa powder on top, blasphemy to American baristas. "If you order a cappuccino in Australia, you get a traditionally dry one, with a really dry top, almost a meringue," says Allie Caran, who leads coffee classes at Toby's Estate, a small-batch Brooklyn-based coffee roaster and cafe.

Eventually, antipodean coffee tastes evolved, and our cousins Down Under began paying more attention to better beans and roasting, but the almost cake-like topping of what they'd come to know as a cappuccino drowned out the nuances of a great cuppa. So some inventive Australian barista decided that it was time to come up with cappuccino-like drink that lets both the milk and coffee shine, and also packs more caffeinated punch than a latte. (New Zealand hotly disputes the Australian origin story, by the way, and claims that it's the birthplace of the flat white.)

But in the States, where cappuccino foam became wetter, not dryer and stiffer, we never found the need for such a drink. Still, Americans have a yen for adopting trends from the Commonwealth. From wetting the parched gullets of Aussies and Kiwis, the flat white eventually made its way to the hip and posh cafes of London, and has been migrating to the U.S. over the last couple years, as everyone from New York to the New York Times to the New York Post to Vogue began declaring it their new favorite coffee drink. But it has yet to make a big splash outside hipster coffeeshops and Australian-themed joints in places like Brooklyn or Austin—even the National Coffee Association hasn't begun tracking it yet.

"It's just so new, we don't have anything on it," NCA spokesman Joseph DeRupo says, confessing he hasn't even tried one yet.

Still, he takes it as evidence of a trend of American consumers flocking toward a wider variety of coffee styles.

"I've never heard of anything coming out of Australia before—or England, for that matter. It's usually the Italian-cafe experience that drives new coffee arrivals," DeRupo says. "It's hard to say that this might be the tip of the iceberg away from Italian coffees, but chances are it'll find its place in the marketplace along with all the other varieties. The more there are, the more people seem to want."

But now that the flat white has made its way to our shores, there's still a lot of debate about what a flat white actually is.

Blue Bottle Coffee director of training Michael Phillips, who was the 2010 World Barista Champion, says that when a customer asks a Blue Bottle barista for a flat white (and it's only Aussies and Kiwis who ask for them, he says), the protocol is to not make a fuss, but to serve a modern American cappuccino, which he says it "incredibly similar" to the flat whites you'll get in, say, New Zealand.

"We'll simply say, 'Absolutely!' but we'll make them a drink that's pretty much our cappuccino," he says. "And if they get the drink and say, 'No, no, no, that's not a flat white,' we'll work with them on it. But in general, they get it and say, 'This is the best flat white I've had in the States.'"

Indeed, the Blue Bottle Coffee at Rockefeller Center in Midtown Manhattan doesn't list the flat white on the menu but will serve it if requested. Just be prepared for the lingering doubts about whether you just got a cappuccino with a new name.

"A flat white is kind of a hotter version of a cappuccino with a lighter layer of foam," Blue Bottle barista Will R. explains.

You'll find yourself in a similar situation at Cafe Medici in Austin, Texas, where, if a customer orders a flat white, barista Maia A. lets him know right off the bat that he's basically getting a smaller latte or milkier cappuccino. The reason, she says, is that the store already makes a cappuccino with lots of microfoam.

"When people ask me for a flat white, I give them a wet cappuccino," she says. "It's sort of like a small latte, and I tell them every time that I'm going to call it that. And the Australians are usually very happy."

"People will argue all day long about what a flat white is," Phillips says. "And as soon as this story is published, every Australian and New Zealander is going to chime in in the comments section and say that this guy has no idea what he's talking about. For them, it's a point of pride."

According to Toby's Estate's Allie Caran, the difference between the flat white and other coffee drinks is subtle but critical. A cappuccino is all about the frothy, big-bubbled layer of milk foam on top of the espresso. A latte is all about the steamed milk, which is added to the espresso and followed by a layer of foam on top. (And a macchiato is kind of a latte in reverse, with the espresso added to the milk.) With a flat white, the star of the show is a very specific stratum of the steamed milk, the luscious microfoam that lies between the steamed milk below and the big bubbles of stiff foam above when a barista riles up a pitcher of milk with a steam wand. This microfoam, which has the sleek, smooth look of latex paint, is poured—not spooned—from a height into a double espresso, ensuring a whole cup full of silky, milky coffee goodness that's kind of like a stronger latte or a wetter, hotter cappuccino, but is also not quite either.

"At the end of the day, all these drinks are just slight variations on flavor and temperature," Caran says. "And that's where people get confused: The volume is the same as a cappuccino, but the texture is like a latte."

The important thing for devotees (mostly a younger "cortado crowd," Caran says) is that they find the flat white smoother, richer, and tastier than its older siblings. And as long as he can get his flat white, Fox, for one, is happy.

"Anytime I need a caffeine boost, I go for a flat white," he says. "It's my drink of choice—whenever it's available."

And just in case you don't feel like a flat white, learn how to brew perfect coffee in a Chemex below: